1. Field of the Invention
The present invention relates to an electrostatic chuck and a manufacturing method of the electrostatic chuck.
2. Description of the Related Art
Heretofore, in the case of manufacturing a semiconductor device, a surface treatment such as deposition and etching has been implemented for a semiconductor wafer. As one of the apparatuses which hold the semiconductor wafer during this surface treatment, there is an electrostatic chuck. This electrostatic chuck has a substrate mounting surface on which a substrate such as the semiconductor wafer is mounted and held, and holds the semiconductor wafer by electrostatic force generated on the substrate mounting surface.
A typical example of the electrostatic chuck includes a base made of ceramics. Moreover, an upper surface of the base becomes the substrate mounting surface on which the substrate such as the wafer is mounted. Furthermore, an electrode for generating the electrostatic force on the substrate mounting surface is embedded in an inside of the base. In addition, a portion from the electrode to the substrate mounting surface in the base becomes a dielectric layer, a portion from the electrode to a lower surface (back surface) of the base becomes a support portion, and the dielectric layer and the support portion are formed integrally across the electrode embedded in the base.
A terminal hole is drilled from the back surface of the base toward the electrode embedded in the base, and a terminal is loaded into this terminal hole, and is brazed to the electrode, whereby the terminal and the electrode are electrically connected to each other.
Such a treatment object holder as described above, in which the electrode is embedded and the electrode and the terminal are electrically connected to each other, is described in Japanese Patent Laid-Open Publication No. 2002-313530.
A thickness of the electrode of the electrostatic chuck is approximately several ten micrometers in general. When the terminal hole is drilled from the back surface of the base toward the electrode in the base, and the terminal is loaded into the terminal hole and bonded to the electrode, it is vital to drill the terminal hole so that the electrode can be exposed to a bottom surface of the terminal hole, and it must be avoided that the terminal hole penetrate the electrode in the thickness direction. Hence, it has been regarded necessary to drill the terminal hole while making a strict control for such drilling.
Moreover, it is necessary that a thickness of the dielectric layer in the base be approximately a few millimeters or less in general to generate the electrostatic force for holding the substrate. Therefore, in such a ceramic base, a portion facing to the terminal hole, of the dielectric layer becomes a portion in which the thickness is the thinnest and strength is the lowest in terms of a structure. when the terminal is loaded into the terminal hole, pressing force is applied to the dielectric layer of a portion in contact with the electrode loaded to the terminal hole. As a result, depending on a pressing force for loading the terminal, there has been an apprehension that a crack may occur in the dielectric layer of the portion to which the pressing force is applied.
The material holder in Japanese Patent Laid-Open Publication No. 2002-313530 described above is one configured to decrease a heating resistance value of a terminal portion of a resistance heating body by adopting a configuration in which the terminal portion is thickened more than a heating portion of the resistance heating body concerned. However, the above-described configuration of the material holder is one to enhance uniform heating performance of the resistance heating body particularly when the electrode is the resistance heating body, and a purpose and usage of the electrode in the above-described configuration differ from those of the electrode configured to generate the electrostatic force of the electrostatic chuck. Therefore, even if the above-described configuration of the material holder is merely used for replacing that of the electrode for generating the electrostatic force of the electrostatic chuck, it has been impossible to sufficiently solve the problems described above.
The present invention is one to advantageously solve the above-described problems. It is an object of the present invention to provide an electrostatic chuck that advantageously suppresses an occurrence of the crack in the dielectric layer in the vicinity of the electrode for generating the electrostatic force, has high reliability, and is easy to manufacture, and to provide a manufacturing method of the electrostatic chuck.